We have a list of 10 numbers from 1 to 10 consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. Now the prime numbers in this list are 2, 3, 5 and 7. We have to remember that 1 is not a prime number as a prime number is a number that has exactly 2 factors. So the numbers that are not prime are 1, 4, 6, 8, 9 and 10. There are 6 such numbers.

If a number is picked at random from this list the possibility of picking a number that is not prime is 6/10 or 3/5 or 60%.